Spark plug



L. J. TETLOW SPARK PLUG Dec. 18, 1934.

Filed Aug. 12, 1929 m n w lewd? J ji'low a Why am Patented Dec. 18, 1934 UNITED, STATES PATENT OFFICE SPARK PLUG Lewis J. Tetlow, Holyoke, Mass.

Application August 12,-

14 Claims.

My invention relates to spark plugs and has for its-principal object the provision of a spark plug thatwillnot only withstand higher pressures than those now available but that will last longer and be more dependable underall conditions of service.

A further object is to provide a more secure and resilient seat for the insulating porcelain body which will give longer life to this fragile element. i

A second specific object is to provide centering means for. the porcelain body, thus insuring not only a standard fit in the seating washer but also a constant predetermined spark gap for any number of spark plugs without entailing any expensive adjustment after the various parts of the plug are assembled.

Another object is to provide a novel non-corroding and dependable means for producing a hotter spark. This comprises a condenser in the form of a mercury filled contact c'up seated on a thin mica or asbestos washer.

Another object is to provide a baffle which not only prevents oil from creeping around the spark gap' thus fouling the plug but which also keeps the carbon-filled burnt oil from covering the nose of the porcelain which would also tend to foul the plug. 9

These and other objects will be made clear by the following description of an embodiment of my invention shown by the accompanying drawing in which 1 4 Figure 1 is a perspective view of the assembled P ug; v

Figure 2 is a longitudinal cross section of the pl s; Y

Figure 3 is a section of the plug at 33 of Figure 2;

Figure 4 is an end View of the plugand;

Figure 5 is a perspective View of the conductor pm. 7 i

In the drawing 1 is the porcelain body shaped to'be held in the metal shell 3 by the coupler nut 2 and provided at the top with a head on which may be spun the contact cap 6. There is also provided in the top a cavity in which is held the elements of thenon-corroding contact.

The contact comprises preferably the end of the conductor pin 13 on which are permanently held one or two copper washers 12 and a washer, 11, made of mica or other insulating material about .004 inches thick on which is seated the inverted cup 9 filled or partly filled with mercury 10. The inverted cup makes electrical contact with the connector cap 6 by means of a pointed pin 22 which is integral with the cup and which fits tightly into a slightly graduated bore in the connector cap 6. If two washers 12 are used a space about 0.004 to 0.006 inch wide is left between them.

1929, Serial No. 385,247

The porcelain body is seated in the main body or shell 3 by means of the usual gasket 17 composed of a copper shell filled with asbestos, but different from the usual practice this gasket is made to seat on a copper shoulder 18 which is drive-fitted in a counter bore in the shoulder of the seat in 3 as shown in Figure 2. I

The body 1 is held against the gasket 17 and seat 18 in the customary manner by the coupler nut 2 which screws into the shell S as shown in Figure 2. Between the nut 2 and insulator l I insert a cush'ion 16 which is a copper ring not of the usual kind but split. This fact permits the ring to adapt itself to any irregularities that might occur either in the porcelain 1 or in the nut 2;

Another feature which I provide is the copper or brass centering rivets 5 best shown in Figure 3. These rivets 5 permit positive centering of the porcelain body 1 thus assuring an exact centering of the wire 13 in the hole 24 of the baiiie 15.v Thetrivets 5 also add greatly to the strength of the porcelain column 1 permitting it to withstand greater side shocks since they form a support almost half way between the ring 16 and the top 6. It is unnecessary to use more than three rivets although more would add somewhat to the strength.

As shown atthe' bottom of Figure 2 and in Figure 4 I provide a baffle which may be secured in any desirable manner as for instance by means of the pin 4 and another pin 23. The baffle closes the mouth of the plug except for the arcuate pas sages 20' and the circular hole 24 in which the pin 13 is centered.

The parts of the plug defined are not in the least complex and may be manufactured with but one or two simple operations. For instance the washers 12 are heated and forced on the rod 13, shrinking as they cool. The rod 13 is covered with a proper cement and dropped intotlie bore through the center of the porcelain body 1 so that the washers fit on the shoulder, a mica washer 11 having first been placed over the end 25 of the rod 13. The cup 9 is filled or partly filled with mercury and the porcelain body being inverted is placed down over the cup so that the end 25 is inside the cup and its edge rests against the mica washer 11, holding the partly filled cup against the washer 11 the porcelain body 1 is righted and the cap 6 forced down over the pin 22. The cap is then spun on the head of the porcelain body and the unit isthen placed in the body 3 on the gasket 1'? which rests on the copper seat 18. The split ring 16 is then put in place and the nut 2 provided with the rivets 5 isfinally firmly screwed down on the ring and the assembly is complete.

The mercury provides a reliable contact between the connector 6-7 and the rod 13 which does not depend upon any mechanical connection or soldered joint. It furthermore, with the insulating mica washer 11, produces a hot spark and does not wear out or corrode with use.

I do not wish to be limited by the particular embodiment and exact arrangement of the structure as described since it will occur to those skilled in the art that other modifications and arrangements employing the same general principles may be used to carry out the invention, but seek to cover by the appended claims all modifications coming fairly within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a spark plug a double seat for the insulator body comprising two separate contacting metal rings, the metal of each ring being softer than the shell of the plug and one of said rings being fixed to the shell.

2. A coupler gland for spark plugs having guide rivets for centering the porcelain body.

3. A coupler nut for spark plugs having centering rivets perpendicular to the axis of the bore of the nut, the heads of said rivets pointing toward said axis.

4. A spark plug for internal combustion engines which comprises a shell, an insulator body, seating means for said body in said shell, 2. gland for holding the body in said shell on said seating means, guide means in the head of said gland, serving to center the body in the shell.

5. A spark plug comprising a shell, a percelain body and a gland, said body having a large center bore at the top connecting with a small center bore, a conductor pin in said small center bore, two spaced washers pressed on the pin near one end and seated in the large bore, a mica washer resting on the outer washer, a cup fitting in said large bore and inverted on said washer, a cap on said body adapted to hold the cup against said washer, the cup being partly filled with mercury.

6. A body for a spark plug comprising a porcelain main part having a connector cap, a conductor rod through the center of the porcelain forming one side of the spark gap and connected to the connector cap through a mercury contact located in the top of the porcelain under the cap, said mercury contact comprising a cup partly filled with mercury and inverted over the end of said rod, a mica washer on said rod, two copper washers pressed on the rod and insulated from the lip of the cup by said mica washer, said cup being of good electrical conducting material and being held against the mica washer by the cap which is fast to the procelain part.

7. In the ignition circuit of an internal combustion engine a mercury contact comprising a porcelain cup lined with a good conducting material, a cap of good conducting material fixed securely over the mouth of said cup, mercury partly filling said cup, a conductor through the bottom of said cup in contact with said mercury but insulated from the lining, the cap making good electrical contact with the mercury.

8. In a spark plug having a spark gap formed between the end of a short pin grounded on the shell and the end of a long pin through the center of the plug, said long pin being of good conductive and non-corrosive material; a porcelain body having a cavity at the top, a connector cap secured to said body to cover said cavity, an inverted cup in said cavity, the conductor pin protruding into said cavity and into said cup, two pressed-on copper washers on the protruding end of the conductor pin, an insulating washer between the lip of the cup and the copper washer, mercury in the cup, means for holding the cup tightly against the insulating washer, said means comprising the said connector cap on said porcelain. v

9. A spark plug comprising a shell, an insulator body and a gland, said body having a large center bore at the top connecting with a small center bore, a conductor pin in said small bore and extending into the larger bore, a washer on the extending portion of the pin and within the larger bore, an insulating washer on the pin above said first mentioned washer, a cup having its rim within said large bore and inverted on said insulating washer, a cap on said body adapted to contact with the cup and to hold the cup against said insulating washer.

' 10. A body for a spark plug comprising an insulator, a conducting pin therethru, a connector cap on said insulator, an inverted cup carried by said cap and extending down over said pin, said cup being spaced from the pin, and an insulating member carried by said pin for closing said cup and insulating the pin from the cup whereby a spark gap is provided between the conductor pin and the inside of the cup.

11. In a spark plug, an outer shell and an insulator body, therein, said shell and body having opposed annular shoulders, the annular edge of the shoulder of said shell being composed of a metal softer than the metal of the rest of the shell and a gasket of the same softness as said edge between the two shoulders and engaging said edge.

12. The device of claim 11 in which said gasket and said edge are of copper and the major portion of the metal of the shell is of steel, whereby irregularities in either of said shoulders are filled by said gasket and edge to make a gas tight joint between the shell and the body when the plug is assembled.

13. A spark plug comprising a shell, a porcelain body, and a gland, said body having a large center bore at the top connecting with a small center bore, a conductor pin in said small center bore, two spaced metal washers pressed on the pin near one end thereof, and within the large bore, an insulating washer resting on the upper washer, a cup in said large bore and inverted on said insulating washer, and a cap on said body connected to said cup, said metal washers being spaced so that the lower washer is seated at the bottom of the larger bore while the upper metal washer holds the insulating washer in firm engagement with the cup.

14. In a spark plug of the type having a spark gap formed between the end of a short pin grounded on the shell and the end of a long pin thru the center of the plug, a porcelain body having a cavity at the top covered by a connector cap, an inverted cup in said cavity, said long pin protruding into said cavity and into said cup, two pressed-on copper washers on the protruding end. of the long pin, and an insulating washer between the rim of the cup and one of the copper washers, said connector cap holding the cup tightly against the insulating washer.

LEWIS J. 'IETLOW. 

